package server;

/*
 * Copyright (c) 1996, 1996, 1997 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * Minor modifications by ML 2001117
 * 
 * CopyrightVersion 1.1_beta
 */

import java.io.*;
import java.net.*;

/**
 * ClassServer is an abstract class that provides the
 * basic functionality of a mini-webserver, specialized
 * to load class files only. A ClassServer must be extended
 * and the concrete subclass should define the getBytes
 * method which is responsible for retrieving the bytecodes
 * for a class.
 *
 * The ClassServer creates a thread that listens on a socket
 * and accepts  HTTP GET requests. The HTTP response contains the
 * bytecodes for the class that requested in the GET header. 
 *
 * For loading remote classes, an RMI application can use a concrete
 * subclass of this server in place of an HTTP server. 
 *
 * @see ClassFileServer
 */
public abstract class ClassServer implements Runnable {

    private ServerSocket server = null;
    private int port;

    /**
     * Constructs a ClassServer that listens on port and
     * obtains a class's bytecodes using the method getBytes.
     *
     * @param port the port number
     * @exception IOException if the ClassServer could not listen
     *            on port.
     */
    protected ClassServer(int port) throws IOException
    {
		this.port = port;
		server = new ServerSocket(port);
		newListener();
    }

    /**
     * Returns an array of bytes containing the bytecodes for
     * the class represented by the argument path.
     * The path is a dot separated class name with
     * the ".class" extension removed.
     *
     * @return the bytecodes for the class
     * @exception ClassNotFoundException if the class corresponding
     * to path could not be loaded.
     * @exception IOException if error occurs reading the class
     */
    public abstract byte[] getBytes(String path) throws IOException, ClassNotFoundException;
    
    /**
     * The "listen" thread that accepts a connection to the
     * server, parses the header to obtain the class file name
     * and sends back the bytecodes for the class (or error
     * if the class is not found or the response was malformed).
     */
    public void run()
    {
		Socket socket;
		System.out.println("Server started : " + server.getInetAddress().getHostAddress() + ":" + port);
		// accept a connection
		try {
		    socket = server.accept();
		} catch (IOException e) {
		    System.out.println("Class Server died: " + e.getMessage());
		    e.printStackTrace();
		    return;
		}

		// create a new thread to accept the next connection
		newListener();

		try {
		    DataOutputStream out = new DataOutputStream(socket.getOutputStream());
		    try {
			// get path to class file from header
			BufferedReader in =
			    new BufferedReader(new InputStreamReader(socket.getInputStream()));
			String path = getPath(in);
			// retrieve bytecodes
			System.out.println("Path Server objects:" + path);
			byte[] bytecodes = getBytes(path);
			// send bytecodes in response (assumes HTTP/1.0 or later)
			try {
			    out.writeBytes("HTTP/1.0 200 OK\r\n");
			    out.writeBytes("Content-Length: " + bytecodes.length +
					   "\r\n");
			    out.writeBytes("Content-Type: application/java\r\n\r\n");
			    out.write(bytecodes);
			    out.flush();
			} catch (IOException ie) {
			    return;
			}
			
		    } catch (Exception e) {
				// write out error response
				out.writeBytes("HTTP/1.0 400 " + e.getMessage() + "\r\n");
				out.writeBytes("Content-Type: text/html\r\n\r\n");
				out.flush();
		    }
			
		} catch (IOException ex) {
		    // eat exception (could log error to log file, but
		    // write out to stdout for now).
		    System.out.println("error writing response: " + ex.getMessage());
		    ex.printStackTrace();
		    
		} finally {
		    try {
		    	socket.close();
		    } catch (IOException e) {}
		}
    }

    /**
     * Create a new thread to listen.
     */
    private void newListener() 
    {
    	(new Thread(this)).start();
    }

    /**
     * Returns the path to the class file obtained from
     * parsing the HTML header.
     */
    private static String getPath(BufferedReader in) throws IOException
    {
		String line = in.readLine();
		String path = "";
		
		// extract class from GET line
		if (line.startsWith("GET /")) {
		    line = line.substring(5, line.length()-1).trim();
	
		    int index = line.indexOf(".class ");
		    if (index != -1) {
			path = line.substring(0, index).replace('/', '.');
		    }
		}
	
		// eat the rest of header
		do {
		    line = in.readLine();
		} while ((line.length() != 0) &&
		         (line.charAt(0) != '\r') && (line.charAt(0) != '\n'));
	
		if (path.length() != 0) {
		    return path;
		} else {
		    throw new IOException("Malformed Header");
		}
    }
}